Op-Amp 741 Based Sound Operated Light Circuit Diagram, Circuit Description with Working Principle and Parts List
In contrast to where so far the technological development has brought us, this project might seem so plain, but it is a basic project that supports advanced projects, helps newcomers in electronics field to understand the fundamentals and being much economical provides extra credits to the users. This mini-project op-amp 741 Based Sound Operate Light builds up a small gadget/device which can be employed to turn on the lights around our surrounding with some triggering activities. And, it can be sound of a clap, or the sound of opening of door or even clicking sound of the key in the lock; it all depends on the sensitivity of the sensor used in the project. We can also utilize this project to catch on intruders following proper installment procedures. The device is provided with a sensitivity adjust control which makes it easier for us to implement in places with desired sound level. Situations where a low sound intensity (whisper) is detected by the device but a high intensity sound of loud bang cannot trigger gadget makes no sense at all. Technologies are developed to increase our comfort level, so does this project. Here, one pulse turns on the light while the other sound pulse will switch it off. Adding this feature avoids distant walk up to the switchboard only to turn on/off the light, also with alternate switching of lights, intruders get really frightened.
Circuit Description of Op-Amp 741 Based Sound Operated Light:-
The Circuit Diagram of Op-amp 741 Based Sound Operated Switch is shown in figure 1. Talking about the components required to build up this device, the list goes on in the following pattern. The core component as seen in the figure is an easily available J-K flip-flop (IC2) who’s output state (Q) drives the coil of relay. An additional op-amp (IC1) is introduced in the circuit which functions as a voltage comparator. The output of IC1 is used to supply clock pulse to the IC2 which is roped in TOGGLE mode. The relay provides AC supply to the electric bulb.
In a similar way, resistors; R2, R3 and the preset P1 supplies a reference voltage which is fed to the non-inverting input of the op-amp. The value of reference voltage can be adjusted by changing the value of preset P1. Looking at the voltage at the inverting terminal of the op-amp, its value is same as the voltage detected across the microphone.
Operation of Op-Amp 741 Based Sound Operated Switch
The device operates in two cases:
In cases where the device doesn’t detect any sound in the vicinity, the voltage across the microphone and inverting terminal is nearly equal to the full dc voltage supplied to the entire circuit i.e. 12V. This eventually leads to low output at the op-amp terminal. In initial conditions, the output of the toggle flip-flop (IC2) is maintained at low state. Because of which, transistor (Q1) operates in cut-off mode and hence relay is de-energised. Corresponding to which the Ac supply to be fed to the electric bulb is interrupted in the mid-way across the relay contacts and the bulb doesn’t glow.
On the contrary, when the device detects sound pulse, the flow of current is initiated in the microphone. The resistor R1 along with the microphone forms the potential divider which causes the voltage across the microphone to fall below +12Vdc. Now, either the bulb glows or not depends entirely upon the intensity of sound level produced. In the non-inverting input of the op-amp, if the detected sound level is sufficient enough to drag the inverting input voltage below the reference voltage, the op-amp generates high output for a small duration. This duration is determined by the duration of sound pulse. Thus generated positive pulse triggers the toggle flip-flop. And, then the output of IC2 reaches high state, the relay is energized. The open contacts of the relay are closed and the AC input supply reaches the bulb and it glows.
However, if the device detects another sound pulse, it toggles the J-K flip-flop and relay contacts open interrupting the supply to the bulb. Due to which the bulb extinguishes.
In circumstances where frequent sound pulses are generated, the bulb state varies back and forth between on and off condition.
|PARTS LIST OF OP-AMP 741 BASED SOUND OPERATED LIGHT|
|R1 = 10 KΩ, 1/4W|
R2 = 1 KΩ, 1/4W
R3 = 470 Ω, 1/4W
R4 = 2.2 KΩ, 1/4W
VR1= 1 KΩ Preset
|D1 = 1N4001 or equivalent
Q1 = 2N2222
IC1 = 741 Op-Amp
IC2 = CD4027B
|TransformerT1 = 220V primary to 12V, 250mA secondary transformer|
MIC1 = Condenser Microphone
RL1 = 12V DC Relay with at least one normally open contact
Switch: S1 (Mains ON/OFF switch)
B1 = 12V Battery
In our project, the significant constraint that needs to be precise and tested is SENSITIVITY. It must be carefully selected and then verified for the project. For large value of reference voltage, the voltage across microphone needs to be varied by small magnitude, so small intensity of sound level is required to alter the state of op-amp output. In a similar way, a smaller reference voltage demands high intensity of sound i.e. loud sound.
With this gadget, there are so many chances of it being triggered by the false alarms and therefore the value of reference voltage must be selected depending upon the sensitivity adjust preset so as to work with intended sound level and generate preferred sound effect. Multiple test activities should be performed recurrently to ensure the reliability of this device.